This invention relates to damper oil control and conservation in open-ended squeeze film shaft dampers which do not include piston ring seals or other end sealing means. More particularly, the invention relates to an internal damper oil reservoir which accommodates inherent fluid pumping conditions in a squeeze film damper to receive oil from, or discharge oil to, opposite ends of the damper squeeze film space when damper conditions warrant, with reduced leakage and air entrainment.
Squeeze film dampers are advantageously applied to high speed turbomachinery including gas turbine engines such as aircraft gas turbine engines in order to damp undesirable radial motion of the rotor shaft of such engines. A typical squeeze film shaft damper may comprise the combination of a rolling element bearing supporting a rotor shaft in which a bearing support member such as the annular outer race of the bearing is fitted in an annular chamber in the bearing supporting housing with permitted limited radial motion in the housing. A thin annular squeeze film space is defined between the outer circumference of the race and the bearing housing. Damper oil under pressure is introduced into the squeeze film space where radial motion of the race and its associated shaft decreases the thickness of the squeeze film and subjects the damper oil to very high pressure and viscous flow.
A rotor shaft imbalance may cause the shaft to undergo an eccentric or orbiting motion which is transmitted to the outer race in the bearing housing. Orbiting motion of the outer race provides an alternating decrease and increase in the squeeze film thickness which generates a high pressure fluid wave moving circumferentially in the annular squeeze film space, with resultant higher and lower pressure regions in the squeeze film space. Under these conditions damper fluid in the high pressure region may leak from the squeeze film through a clearance gap between the bearing support member and housing. On the other hand, the low pressure region in the squeeze film space may cause air to be drawn into the squeeze film through the same clearance gap, thereby diminishing damping effectiveness. A system of conserving and re-supplying existing and available damper oil would increase damper effectiveness.
It is therefore an object of this invention to provide improved internal oil control and oil conservation in a squeeze film damper.
It is another object of this invention to provide improved oil receiving and supplying reservoir channels open to direct flow from opposite ends of the annular squeeze film space of a squeeze film damper.
It is a further object of this invention to provide a squeeze film damper with circumferential oil reservoir channels concentrically adjacent with the squeeze film space of the damper and in open axial fluid flow communication therewith.
It is another object of this invention to isolate a high pressure region in the squeeze film from a clearance gap through which oil can escape.
It is another object of this invention to isolate a low pressure region in the squeeze film from a clearance gap through which air can be entrained in the squeeze film.
It is another object of this invention to direct oil exiting the high pressure region in a squeeze film space away from leakage points and direct the oil to re-supply a low pressure region of the squeeze film space.